collisions got bugged upon recreating the file. you can try to fix it with double-collision method. search for the guide, it was posted several times.
in short: collision object should be dismissed, cloned, set with no "deformation" option on vertices format, then grouped with original and converted back to COL compound.
P.S. when you "change nothing" on a model, it does not mean you should get exactly the same model file on export. ZModeler re-creates model file from zero up using data in scene. It could create some components of YFT file in a different manner than original model had, so you get a completely new YFT file on export. It happens some features are not retained perfectly and could be bugged.